1. Field of the Invention
This invention relates to color display devices and methods, and more particularly to color display devices in which input white light is color code for transmittance through the display.
2. Description of the Related Art
A conventional method for achieving full color performance in a color display such as a backlit, transmissive flat-panel matrix display employs a repeated series of red, green and blue transmissive filter stripes to color code incident white light. The white light passes through the absorptive dye filter stripes, which transmit the filter color but absorb other colors. The matrix display likewise consists of a repeated series of red, green and blue information containing lines. The filter stripes are precisely registered with respect to the matrix display so that the red, green and blue light emerging from the filters pass through the red, green and blue information-containing stripes of the matrix display, respectively. A typical display may have 525 color lines, which are visually integrated by the viewer to produce a full color image.
One of the principal drawbacks of this approach is that each filter stripe absorbs light outside of its pass band. Thus, most of the light which is directed onto the display device will generally be absorbed and never displayed, resulting in a reduced output intensity and/or the need for light enhancement apparatus. Furthermore, the observer's eye has to integrate the intensities of the three color display stripes to perceive the desired color hue. This limits the resolution of the display. The complicated lithographic process associated with deposition of the color stripes adds additional complexity to the process.
It is also possible to provide a full color display from a monochromatic CRT by means of one or more color light valves which respond to the CRT output. In one approach three CRTs are employed with three separate light valves and associated optics to produce an integrated full color display. The system requires a large amount of equipment and coordination, and is expensive and complicated. Another approach uses three one-inch CRTS to address a two-inch light valve with optics that combine the three primary color images on the screen. Still another approach involves a sequential addressing of a CRT/light valve combination by the red, green and blue fields, and synchronous rotation of a color wheel in front of a light valve. To accomplish this, a very fast CRT/light valve combination is needed in addition to a three field memory. More than two-thirds of the light is lost in the system and fails to appear on the output display.